At present, in hand-held mowers (shears) and backpack-type lawn and garden machines, conventional two-stroke and four-stroke small-size general-purpose engines have been widely used, requiring operating personnel to hold the device with the hands or bear on the back during operation.
An engine usually includes a cylinder, a carburetor disposed at one side of the cylinder, and a carburetor base disposed between the carburetor and the cylinder. An air inlet channel is disposed on the carburetor base, so that liquid oil enters the cylinder after being vapourized by the carburetor. Furthermore, a pulsation hole is also disposed on the carburetor, negative pressure generated due to reciprocating motion of a piston being transferred into the carburetor through the pulsation hole to drive the carburetor to run up. A pulsation hole channel is disposed on the carburetor base. The pulsation hole channel is connected between the air inlet channel on the carburetor base and the pulsation hole, so as to introduce a negative pressure power inside the air inlet channel into the pulsation hole. However, the existing pulsation hole channel is directly connected to the air inlet channel on the carburetor base; in this way, the oil and gas in the air inlet channel is very easily liquefied to thereby block the cooling of the engine, so that the carburetor cannot run up stably.